Landslide hazard cascades can trigger earthquakes

While earthquakes are well-known to trigger surface hazards and initiate hazard cascades, whether surface hazards can instead trigger earthquakes remains underexplored. In 2018, two landslides on the Tibetan plateau created landslide-dammed lakes which subsequently breached and caused catastrophic outburst floods. Here we build an earthquake catalog using machine-learning and cross-correlation-based methods which shows there was a statistically significant increase in earthquake activity (local magnitude ≤ 2.6) as the landslide-dammed lake approached peak water level which returned to the background level after dam breach. We further find that ~90% of the seismicity occurred where Coulomb stress increased due to the combined effect of direct loading and pore pressure diffusion. The close spatial and temporal correlation between the calculated Coulomb stress increase and earthquake activity suggests that the earthquakes were triggered by these landslide hazard cascades. Finally, our Coulomb stress modeling considering the properties of landslide-dammed lakes and reservoir-induced earthquakes globally suggests that earthquake triggering by landslide-dammed lakes and similar structures may be a ubiquitous phenomenon. Therefore, we propose that earthquake-surface hazard interaction can include bidirectional triggering which should be properly accounted for during geological hazard assessment and management in mountainous regions.

. For the earthquake sequence which occurred within 10 km of the landslide-dammed lake (LDL) as the second LDL approached peak water level, the first motions of the two largest earthquakes (ML 2.6 (a) and ML 1.9 (b)) at surrounding seismic stations are marked.Black and white dots represent upward and downward first motions, respectively.Empirically derived statistic 99.71% 99.71% 99.71% * 1 week (10 to 16 November, 2018) when the second landslide-dammed lake (LDL) approached its peak water level ** look-ahead time from 0.5 to 3 days, confidence probability of 0.9, effective min magnitude cutoff of 1.1, the increase in lower cutoff magnitude during clusters of 0, and the number of crack radii surrounding each earthquake of 5 *** look-ahead time from 1 to 10 days, confidence probability of 0.95, effective min magnitude cutoff of 1.5, the increase in lower cutoff magnitude during clusters of 0.5, and the number of crack radii surrounding each earthquake of 10 Figures S1 to S18TableS1

Fig. S1 |
Fig. S1 | Sentinel-2 images covering the 2018 Baige landslides (source: the Copernicus Data Space Ecosystem).Dashed yellow and red lines outline the landslides and dams in b, c, and d.The times of these images are displayed in yyyy-mm-dd format in each panel.

Fig. S2 |
Fig. S2 | Cumulative number of earthquakes, daily seismicity rate, earthquake magnitudes, and landslide-dammed lake water level over a twenty-day period.Gray dashed line in (c) marks the magnitude of completeness.
Fig. S3 | Local magnitude of earthquakes within 10 km of the Baige landslide-dammed lakes (LDLs) over a five-year period.Gray bar marks the week (from 10 to 16 November, 2018) when the second LDL approached its peak water level.

Fig. S4 |
Fig. S4 | Distribution of ML>2.5 earthquakes near the Baige landslides from May 2018 to November 2018.Times and magnitudes of the earthquakes are indicated.

Fig. S5 |
Fig. S5 | Earthquakes after performing declustering.a Distribution of earthquakes from May 2018 to January 2023 within 10 km from landslide-dammed lakes (LDLs).Red and blue dots represent the locations of earthquakes that were left and removed after performing declustering, respectively.b Earthquake magnitudes and LDL water level over a twenty-day period.c Earthquake depths over a twenty-day period.

Fig. S6 |
Fig. S6 | Number of earthquakes in a given 1-week time window using the earthquakes from May 2018 to January 2023.The inset figure zooms into a region of the histogram with smaller values.

Fig. S8 |
Fig. S8 | Earthquake depths in complete catalog (a) and in catalog before template matching (b) over an eight-day period.Median earthquake depths in complete catalog and in catalog before template matching are 1.19 and 1.24 km, respectively.

Fig. S10 |
Fig. S10 | Coulomb stress change (∆CFS) map at depth of 4.5 km corresponding to -0.5 km asl, 11 days after the formation of a 30-m deep landslide-dammed lake (LDL).∆CFS on the surrounding normal (a) and reverse (b) fault systems due to the LDL's direct gravitational loading and pore pressure diffusion.